In three-dimensional printing, building materials are selectively jetted from one or more printing heads or dispensers and deposited onto a fabrication tray in consecutive layers according to pre-determined image data. The layers may include cross sections of the three-dimensional object to be formed and of a support construction that is later removed from the finished object. The building materials may be UV polymerizable compositions, e.g. photopolymers, which are polymerized, solidified, conditioned or cured after deposition, for example, by ultraviolet (UV) radiation.
Prior to solidifying the layer, a leveling device may remove a surplus portion of the material dispensed in the layers. The collected surplus material is generally disposed of as waste inherent to the printing process.
It is common practice to perform a periodic maintenance process during the printing process, for example “purging” of the printing heads, e.g. once every 10 minutes, depending on the materials being used and other system characteristics. This procedure is intended to flush the printing heads and in this way reduce the risk of nozzles clogging. Nozzle clogging maybe the result of for example dust accumulation, remnants of solidified material that may accumulate within and/or around the nozzle orifices of the printing head, i.e. on the orifice plate, for example due to proximity of a UV light source and/or reflection of UV light. The printing head is moved to a purge unit where building material is provided to the nozzles and discharged from the nozzles so that material elements clogging the nozzle orifices and/or accumulating on the orifice plate may be removed together with the material used for the purging process. The purged material is collected and considered as waste, to be disposed of together with the waste collected from the leveling device.
It may not be desirable, e.g. for environmental reasons, to dispose of such waste by using standard methods as a sewerage system or a municipal waste removal service, and laws or regulations may prohibit this as well. Instead, the waste material for disposal should be pre-treated and/or fully cured and safely disposed of.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. Moreover, some of the blocks depicted in the drawings may be combined into a single function.